U.S. patent number 11,223,370 [Application Number 16/065,676] was granted by the patent office on 2022-01-11 for method and apparatus for transmitting information.
This patent grant is currently assigned to LG Electronics Inc.. The grantee listed for this patent is LG Electronics Inc.. Invention is credited to Bonghoe Kim, Kwangseok Noh.
United States Patent |
11,223,370 |
Noh , et al. |
January 11, 2022 |
Method and apparatus for transmitting information
Abstract
In a wireless communication system, a transmission device
inputs, in some of N input bit positions of a polar code having the
size N, input bits including D-bit information and X-bit user
equipment (UE) ID according to a predetermined bit allocation
sequence. The transmission device encodes the input bits by using
the polar code. The transmission device transmits an encoded output
sequence.
Inventors: |
Noh; Kwangseok (Seoul,
KR), Kim; Bonghoe (Seoul, KR) |
Applicant: |
Name |
City |
State |
Country |
Type |
LG Electronics Inc. |
Seoul |
N/A |
KR |
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Assignee: |
LG Electronics Inc. (Seoul,
KR)
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Family
ID: |
1000006044597 |
Appl.
No.: |
16/065,676 |
Filed: |
February 14, 2018 |
PCT
Filed: |
February 14, 2018 |
PCT No.: |
PCT/KR2018/001980 |
371(c)(1),(2),(4) Date: |
June 22, 2018 |
PCT
Pub. No.: |
WO2018/151555 |
PCT
Pub. Date: |
August 23, 2018 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20210203361 A1 |
Jul 1, 2021 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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62460535 |
Feb 17, 2017 |
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62504486 |
May 10, 2017 |
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62507118 |
May 16, 2017 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H03M
13/13 (20130101); H04L 1/0061 (20130101) |
Current International
Class: |
H03M
13/13 (20060101); H04L 1/00 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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WO201700023079 |
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Feb 2017 |
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WO |
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Other References
AT&T, "Polar Code Design for DCI," 3GPP TSG RAN WG1 Meeting
#88, dated Feb. 13-17, 2017, 4 pages. cited by applicant .
Coherent Logix Inc., "Eady block discrimination with polar codes to
further accelerate DCI blind detection," 3GPP TSG RAN WG1 Meeting
#88, dated Feb. 13-17, 2017, 6 pages. cited by applicant .
Huawei et al., "Performance evaluation of channel coding schemes
for collrol channel," 3GPP TSG RAN WG1 Meeting #87, dated Nov.
14-18, 2016, 12 pages. cited by applicant .
Intel Corporation, "Design aspects of Polar Code for control
channels," 3GPP TSG RAN WG1 Meeting #88, dated Feb. 13-17, 2017, 5
pages. cited by applicant .
International Search Report in International Application No.
PCT/KR2018/001980, dated Jul. 3, 2018, 11 pages. cited by
applicant.
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Primary Examiner: Nguyen; Thien
Attorney, Agent or Firm: Fish & Richardson P.C.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a National Stage application under 35 U.S.C.
.sctn. 371 of International Application No. PCT/KR2018/001980,
filed on Feb. 14, 2018, which claims the benefit of U.S.
Provisional Application No. 62/507,118, filed on May 16, 2017, U.S.
Provisional Application No. 62/504,486, filed on May 10, 2017, and
U.S. Provisional Application No. 62/460,535, filed on Feb. 17,
2017. The disclosures of the prior applications are incorporated by
reference in their entirety.
Claims
The invention claimed is:
1. A method of transmitting information by a transmitting device in
a wireless communication system, the method comprising: inputting
input bits including (i) D-bit information and (ii) an X-bit user
equipment (UE) ID to a part of N input bit positions of a size-N
polar code according to a specific bit allocation sequence;
encoding the input bits using the polar code; and transmitting an
encoded output sequence, wherein the N input bit positions include
(i) D input bit positions having highest reliabilities among the N
input bit positions and (ii) N-D frozen bit positions other than
the D input bit positions, wherein the X-bit UE ID is input to X
input bit positions among the D input bit positions, and wherein
D-X bits among the D-bit information are input to D-X input bit
positions except for the X input bit positions among the D input
bit positions, and remaining X bits among the D-bit information are
input to X frozen bit positions having highest reliabilities among
the N-D frozen bit positions.
2. The method according to claim 1, wherein the other remaining
part of the D-bit information is an end part of the D-bit
information.
3. The method according to claim 1, wherein the UE ID is a UE ID of
the transmitting device or a UE ID of a receiving device which is a
destination of the D-bit information.
4. A transmitting device for transmitting information in a wireless
communication system, the transmitting device comprising, a radio
frequency (RF) transceiver; a processor, and a memory storing at
least one program that causes the processor to perform operations
comprising: inputting input bits including (i) D-bit information
and (ii) an X-bit user equipment (UE) ID to a part of N input bit
positions of a size-N polar code according to a specific bit
allocation sequence; encoding the input bits using the polar code;
and transmitting an encoded output sequence, wherein the N input
bit positions include (i) D input bit positions having highest
reliabilities among the N input bit positions and (ii) N-D frozen
bit positions other than the D input bit positions, wherein the
X-bit UE ID is input to X input bit positions among the D input bit
positions, and wherein a part of the D-bit information is input to
D-X input bit positions except for the X input bit positions among
the D input bit positions, and a remaining part of the D-bit
information is input to frozen bit positions having highest
reliabilities among the N-D frozen bit positions.
5. The transmitting device according to claim 4, wherein the
remaining part of the D-bit information is an end part of the D-bit
information.
6. The transmitting device according to claim 4, wherein the UE ID
is a UE ID of the transmitting device or a UE ID of a receiving
device which is a destination of the D-bit information.
Description
TECHNICAL FIELD
The present invention relates to a wireless communication system
and, more particularly, to a method and apparatus for transmitting
information.
BACKGROUND ART
With appearance and spread of machine-to-machine (M2M)
communication, machine type communication (MTC) and a variety of
devices such as smartphones and tablet Personal Computers (PCs) and
technology demanding a large amount of data transmission, data
throughput needed in a cellular network has rapidly increased. To
satisfy such rapidly increasing data throughput, carrier
aggregation technology, cognitive radio technology, etc. for
efficiently employing more frequency bands and multiple input
multiple output (MIMO) technology, multi-base station (BS)
cooperation technology, etc. for raising data capacity transmitted
on limited frequency resources have been developed.
As more communication devices have demanded higher communication
capacity, there has been necessity of enhanced mobile broadband
(eMBB) relative to legacy radio access technology (RAT). In
addition, massive machine type communication (mMTC) for providing
various services anytime and anywhere by connecting a plurality of
devices and objects to each other is one main issue to be
considered in future-generation communication.
Further, a communication system to be designed in consideration of
services/UEs sensitive to reliability and latency is under
discussion. The introduction of future-generation RAT has been
discussed by taking into consideration eMBB communication, mMTC,
ultra-reliable and low-latency communication (URLLC), and the
like.
DISCLOSURE
Technical Problem
Due to introduction of new radio communication technology, the
number of user equipments (UEs) to which a BS should provide a
service in a prescribed resource region increases and the amount of
data and control information that the BS should transmit to the UEs
increases. Since the amount of resources available to the BS for
communication with the UE(s) is limited, a new method in which the
BS efficiently receives/transmits uplink/downlink data and/or
uplink/downlink control information using the limited radio
resources is needed. In other words, as the density of nodes and/or
the density of UEs increases, a method of efficiently using
high-density nodes or high-density UEs for communication is
needed.
With development of technologies, overcoming delay or latency has
become an important challenge. Applications whose performance
critically depends on delay/latency are increasing. Accordingly, a
method to reduce delay/latency compared to the legacy system is
demanded.
In addition, with development of smart devices, a new method of
efficiently transmitting/receiving small volumes of data or
efficiently transmitting/receiving data generated with a low
frequency is needed.
Furthermore, with advances in technology, use of frequency bands
that have not conventionally used has been discussed. Since newly
introduced frequency bands differ in characteristics from legacy
frequency bands, it is difficult to apply legacy communication
technology to newly introduced communication technology. Hence,
introduction of communication technology suitable for frequency
bands used for new communication is required.
The technical objects that can be achieved through the present
invention are not limited to what has been particularly described
hereinabove and other technical objects not described herein will
be more clearly understood by persons skilled in the art from the
following detailed description.
Technical Solution
According to an aspect of the present invention, provided herein is
a method of transmitting information by a transmitting device in a
wireless communication system. The method includes: inputting input
bits including D-bit information and an X-bit user equipment (UE)
ID to a part of N input bit positions of a size-N polar code
according to a specific bit allocation sequence; encoding the input
bits using the polar code; and transmitting an encoded output
sequence.
According to another aspect of the present invention, provided
herein is a transmitting device for transmitting information in a
wireless communication system. The transmitting device includes a
radio frequency (RF) unit, and a processor configured to control
the RF unit. The processor may be configured to: input input bits
including D-bit information and an X-bit user equipment (UE) ID to
a part of N input bit positions of a size-N polar code according to
a specific bit allocation sequence; encode the input bits using the
polar code; and control the RF unit to transmit an encoded output
sequence.
In each aspect of the present invention, the N input bit positions
may be divided into information bit positions and frozen bit
positions. The information bit positions may be D input bit
positions having high reliabilities among the N input bit
positions. The UE ID may be input to input position(s) having high
reliabilities among the frozen bit positions.
In each aspect of the present invention, the UE ID may be input to
X information bit positions among the information bit
positions.
In each aspect of the present invention, a part of the D-bit
information may be input to remaining information bit positions
except for the X information bit positions to which the UE ID is
input among the information bit positions and the other information
bit(s) among the D-bit information may be input to frozen bit
position(s) having high reliabilities among the frozen bit
positions.
In each aspect of the present invention, the other information
bit(s) may be information bit(s) corresponding to the information
bit positions to which the UE ID is input among the D-bit
information.
In each aspect of the present invention, the other information
bit(s) may be information bit(s) positioned at an end of the D-bit
information.
In each aspect of the present invention, the UE ID may be a UE ID
of the transmitting device or a UE ID of a receiving device which
is a destination of the D-bit information.
The above technical solutions are merely some parts of the
embodiments of the present invention and various embodiments into
which the technical features of the present invention are
incorporated can be derived and understood by persons skilled in
the art from the following detailed description of the present
invention.
Advantageous Effects
According to an example of the present invention, uplink/downlink
signals can be efficiently transmitted/received. Therefore, overall
throughput of a radio communication system can be improved.
According to an example of the present invention, delay/latency
occurring during communication between a user equipment and a base
station may be reduced.
In addition, it is possible to efficiently transmit/receive not
only a small amount of data but also data which occurs
infrequently.
In addition, signals can be transmitted/received efficiently and at
a low error rate in a wireless communication system.
It will be appreciated by persons skilled in the art that that the
effects that can be achieved through the present invention are not
limited to what has been particularly described hereinabove and
other advantages of the present invention will be more clearly
understood from the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are included to provide a further
understanding of the invention, illustrate embodiments of the
invention and together with the description serve to explain the
principle of the invention.
FIG. 1 illustrates a transport block processing procedure in an
LTE/LTE-A system.
FIG. 2 is a block diagram illustrating rate matching performed by
separating an encoded code block into a systematic part and a
parity part.
FIG. 3 illustrates an internal structure of a circular buffer.
FIG. 4 is a block diagram for a polar code encoder.
FIG. 5 illustrates the concept of channel combining and channel
splitting for channel polarization.
FIG. 6 illustrates N-th level channel combining for a polar
code.
FIG. 7 illustrates an evolution of decoding paths in a list-L
decoding process.
FIG. 8 illustrates the concept of selecting position(s) to which
information bit(s) are to be allocated in polar codes.
FIG. 9 illustrates puncturing and information bit allocation
according to the present invention.
FIG. 10 illustrates a polar encoding process and a polar decoding
process of the present invention for improving a false alarm ratio
(FAR).
FIG. 11 illustrates block error ratio (BLER) performance and an
early termination probability for polar encoding/decoding according
to the present invention.
FIG. 12 illustrates sequences in which reserved or known bit(s) of
the present invention are included.
FIG. 13 is a block diagram illustrating elements of a transmitting
device 10 and a receiving device 20 for implementing the present
invention.
MODE FOR CARRYING OUT THE INVENTION
Reference will now be made in detail to the exemplary embodiments
of the present invention, examples of which are illustrated in the
accompanying drawings. The detailed description, which will be
given below with reference to the accompanying drawings, is
intended to explain exemplary embodiments of the present invention,
rather than to show the only embodiments that can be implemented
according to the invention. The following detailed description
includes specific details in order to provide a thorough
understanding of the present invention. However, it will be
apparent to those skilled in the art that the present invention may
be practiced without such specific details.
In some instances, known structures and devices are omitted or are
shown in block diagram form, focusing on important features of the
structures and devices, so as not to obscure the concept of the
present invention. The same reference numbers will be used
throughout this specification to refer to the same or like
parts.
The following techniques, apparatuses, and systems may be applied
to a variety of wireless multiple access systems. Examples of the
multiple access systems include a code division multiple access
(CDMA) system, a frequency division multiple access (FDMA) system,
a time division multiple access (TDMA) system, an orthogonal
frequency division multiple access (OFDMA) system, a single carrier
frequency division multiple access (SC-FDMA) system, and a
multicarrier frequency division multiple access (MC-FDMA) system.
CDMA may be embodied through radio technology such as universal
terrestrial radio access (UTRA) or CDMA2000. TDMA may be embodied
through radio technology such as global system for mobile
communications (GSM), general packet radio service (GPRS), or
enhanced data rates for GSM evolution (EDGE). OFDMA may be embodied
through radio technology such as institute of electrical and
electronics engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX),
IEEE 802.20, or evolved UTRA (E-UTRA). UTRA is a part of a
universal mobile telecommunications system (UMTS). 3rd generation
partnership project (3GPP) long term evolution (LTE) is a part of
evolved UMTS (E-UMTS) using E-UTRA. 3GPP LTE employs OFDMA in DL
and SC-FDMA in UL. LTE-advanced (LTE-A) is an evolved version of
3GPP LTE. For convenience of description, it is assumed that the
present invention is applied to 3GPP based communication system,
e.g. LTE/LTE-A, NR. However, the technical features of the present
invention are not limited thereto. For example, although the
following detailed description is given based on a mobile
communication system corresponding to a 3GPP LTE/LTE-A/NR system,
aspects of the present invention that are not specific to 3GPP
LTE/LTE-A/NR are applicable to other mobile communication
systems.
In examples of the present invention described below, the term
"assume" may mean that a subject to transmit a channel transmits
the channel in accordance with the corresponding "assumption". This
may also mean that a subject to receive the channel receives or
decodes the channel in a form conforming to the "assumption", on
the assumption that the channel has been transmitted according to
the "assumption".
In the present invention, a user equipment (UE) may be a fixed or
mobile device. Examples of the UE include various devices that
transmit and receive user data and/or various kinds of control
information to and from a base station (BS). The UE may be referred
to as a terminal equipment (TE), a mobile station (MS), a mobile
terminal (MT), a user terminal (UT), a subscriber station (SS), a
wireless device, a personal digital assistant (PDA), a wireless
modem, a handheld device, etc. In addition, in the present
invention, a BS generally refers to a fixed station that performs
communication with a UE and/or another BS, and exchanges various
kinds of data and control information with the UE and another BS.
The BS may be referred to as an advanced base station (ABS), a
node-B (NB), an evolved node-B (eNB), a base transceiver system
(BTS), an access point (AP), a processing server (PS), etc.
Particularly, a BS of a UTRAN is referred to as a Node-B, a BS of
an E-UTRAN is referred to as an eNB, and a BS of a new radio access
technology network is referred to as an eNB. In describing the
present invention, a BS will be referred to as an eNB.
In the present invention, a node refers to a fixed point capable of
transmitting/receiving a radio signal through communication with a
UE. Various types of eNBs may be used as nodes irrespective of the
terms thereof. For example, a BS, a node B (NB), an e-node B (eNB),
a pico-cell eNB (PeNB), a home eNB (HeNB), eNB, a relay, a
repeater, etc. may be a node. In addition, the node may not be an
eNB. For example, the node may be a radio remote head (RRH) or a
radio remote unit (RRU). The RRH or RRU generally has a lower power
level than a power level of an eNB. Since the RRH or RRU
(hereinafter, RRH/RRU) is generally connected to the eNB through a
dedicated line such as an optical cable, cooperative communication
between RRH/RRU and the eNB can be smoothly performed in comparison
with cooperative communication between eNBs connected by a radio
line. At least one antenna is installed per node. The antenna may
mean a physical antenna or mean an antenna port or a virtual
antenna.
In the present invention, a cell refers to a prescribed
geographical area to which one or more nodes provide a
communication service. Accordingly, in the present invention,
communicating with a specific cell may mean communicating with an
eNB or a node which provides a communication service to the
specific cell. In addition, a DL/UL signal of a specific cell
refers to a DL/UL signal from/to an eNB or a node which provides a
communication service to the specific cell. A node providing UL/DL
communication services to a UE is called a serving node and a cell
to which UL/DL communication services are provided by the serving
node is especially called a serving cell. Furthermore, channel
status/quality of a specific cell refers to channel status/quality
of a channel or communication link formed between an eNB or node
which provides a communication service to the specific cell and a
UE. In the 3GPP based communication system, the UE may measure DL
channel state received from a specific node using cell-specific
reference signal(s) (CRS(s)) transmitted on a CRS resource and/or
channel state information reference signal(s) (CSI-RS(s))
transmitted on a CSI-RS resource, allocated by antenna port(s) of
the specific node to the specific node.
Meanwhile, a 3GPP based communication system uses the concept of a
cell in order to manage radio resources and a cell associated with
the radio resources is distinguished from a cell of a geographic
region.
A "cell" of a geographic region may be understood as coverage
within which a node can provide service using a carrier and a
"cell" of a radio resource is associated with bandwidth (BW) which
is a frequency range configured by the carrier. Since DL coverage,
which is a range within which the node is capable of transmitting a
valid signal, and UL coverage, which is a range within which the
node is capable of receiving the valid signal from the UE, depends
upon a carrier carrying the signal, the coverage of the node may be
associated with coverage of the "cell" of a radio resource used by
the node. Accordingly, the term "cell" may be used to indicate
service coverage of the node sometimes, a radio resource at other
times, or a range that a signal using a radio resource can reach
with valid strength at other times.
Meanwhile, the 3GPP communication standards use the concept of a
cell to manage radio resources. The "cell" associated with the
radio resources is defined by combination of downlink resources and
uplink resources, that is, combination of DL CC and UL CC. The cell
may be configured by downlink resources only, or may be configured
by downlink resources and uplink resources. If carrier aggregation
is supported, linkage between a carrier frequency of the downlink
resources (or DL CC) and a carrier frequency of the uplink
resources (or UL CC) may be indicated by system information. For
example, combination of the DL resources and the UL resources may
be indicated by linkage of system information block type 2 (SIB2).
The carrier frequency means a center frequency of each cell or CC.
A cell operating on a primary frequency may be referred to as a
primary cell (Pcell) or PCC, and a cell operating on a secondary
frequency may be referred to as a secondary cell (Scell) or SCC.
The carrier corresponding to the Pcell on downlink will be referred
to as a downlink primary CC (DL PCC), and the carrier corresponding
to the Pcell on uplink will be referred to as an uplink primary CC
(UL PCC). A Scell means a cell that may be configured after
completion of radio resource control (RRC) connection establishment
and used to provide additional radio resources. The Scell may form
a set of serving cells for the UE together with the Pcell in
accordance with capabilities of the UE. The carrier corresponding
to the Scell on the downlink will be referred to as downlink
secondary CC (DL SCC), and the carrier corresponding to the Scell
on the uplink will be referred to as uplink secondary CC (UL SCC).
Although the UE is in RRC-CONNECTED state, if it is not configured
by carrier aggregation or does not support carrier aggregation, a
single serving cell configured by the Pcell only exists.
3GPP based communication standards define DL physical channels
corresponding to resource elements carrying information derived
from a higher layer and DL physical signals corresponding to
resource elements which are used by a physical layer but which do
not carry information derived from a higher layer. For example, a
physical downlink shared channel (PDSCH), a physical broadcast
channel (PBCH), a physical multicast channel (PMCH), a physical
control format indicator channel (PCFICH), a physical downlink
control channel (PDCCH), and a physical hybrid ARQ indicator
channel (PHICH) are defined as the DL physical channels, and a
reference signal and a synchronization signal are defined as the DL
physical signals. A reference signal (RS), also called a pilot,
refers to a special waveform of a predefined signal known to both a
BS and a UE. For example, a cell-specific RS (CRS), a UE-specific
RS (UE-RS), a positioning RS (PRS), and channel state information
RS (CSI-RS) may be defined as DL RSs. Meanwhile, the 3GPP based
communication standards define UL physical channels corresponding
to resource elements carrying information derived from a higher
layer and UL physical signals corresponding to resource elements
which are used by a physical layer but which do not carry
information derived from a higher layer. For example, a physical
uplink shared channel (PUSCH), a physical uplink control channel
(PUCCH), and a physical random access channel (PRACH) are defined
as the UL physical channels, and a demodulation reference signal
(DM RS) for a UL control/data signal and a sounding reference
signal (SRS) used for UL channel measurement are defined as the UL
physical signals.
In the present invention, a physical downlink control channel
(PDCCH), a physical control format indicator channel (PCFICH), a
physical hybrid automatic retransmit request indicator channel
(PHICH), and a physical downlink shared channel (PDSCH) refer to a
set of time-frequency resources or resource elements (REs) carrying
downlink control information (DCI), a set of time-frequency
resources or REs carrying a control format indicator (CFI), a set
of time-frequency resources or REs carrying downlink
acknowledgement (ACK)/negative ACK (NACK), and a set of
time-frequency resources or REs carrying downlink data,
respectively. In addition, a physical uplink control channel
(PUCCH), a physical uplink shared channel (PUSCH) and a physical
random access channel (PRACH) refer to a set of time-frequency
resources or REs carrying uplink control information (UCI), a set
of time-frequency resources or REs carrying uplink data and a set
of time-frequency resources or REs carrying random access signals,
respectively. In the present invention, in particular, a
time-frequency resource or RE that is assigned to or belongs to
PDCCH/PCFICH/PHICH/PDSCH/PUCCH/PUSCH/PRACH is referred to as
PDCCH/PCFICH/PHICH/PDSCH/PUCCH/PUSCH/PRACH RE or
PDCCH/PCFICH/PHICH/PDSCH/PUCCH/PUSCH/PRACH time-frequency resource,
respectively. Therefore, in the present invention,
PUCCH/PUSCH/PRACH transmission of a UE is conceptually identical to
UCI/uplink data/random access signal transmission on
PUSCH/PUCCH/PRACH, respectively. In addition,
PDCCH/PCFICH/PHICH/PDSCH transmission of an eNB is conceptually
identical to downlink data/DCI transmission on
PDCCH/PCFICH/PHICH/PDSCH, respectively.
For terms and technologies which are not described in detail in the
present invention, reference can be made to the standard document
of 3GPP LTE/LTE-A, for example, 3GPP TS 36.211, 3GPP TS 36.212,
3GPP TS 36.213, 3GPP TS 36.321, and 3GPP TS 36.331 and the standard
document of 3GPP NR, for example, 3GPP TS 38.xxx. In addition, as
to polar codes and the principle of encoding and decoding using the
polar codes, reference may be made to `E. Arikan, "Channel
Polarization: A Method for Constructing Capacity-Achieving Codes
for Symmetric Binary-Input Memoryless Channels," in IEEE
Transactions on Information Theory, vol. 55, no. 7, pp. 3051-3073,
July 2009`.
As more communication devices have demanded higher communication
capacity, there has been necessity of enhanced mobile broadband
relative to legacy radio access technology (RAT). In addition,
massive machine type communication for providing various services
irrespective of time and place by connecting a plurality of devices
and objects to each other is one main issue to be considered in
future-generation communication. Further, a communication system
design in which services/UEs sensitive to reliability and latency
are considered is under discussion. The introduction of
future-generation RAT has been discussed by taking into
consideration enhanced mobile broadband communication, massive MTC,
ultra-reliable and low-latency communication (URLLC), and the like.
In current 3GPP, a study of the future-generation mobile
communication system after EPC is being conducted. In the present
invention, the corresponding technology is referred to as a new RAT
(NR) or 5G RAT, for convenience.
An NR communication system demands that much better performance
than a legacy fourth generation (4G) system be supported in terms
of data rate, capacity, latency, energy consumption, and cost.
Accordingly, the NR system needs to make progress in terms of
bandwidth, spectrum, energy, signaling efficiency, and cost per
bit. NR needs to use efficient waveforms in order to satisfy these
requirements.
FIG. 1 illustrates a transport block processing procedure in an
LTE/LTE-A system.
In order for a receiving side to correct errors that a channel
experiences, a transmitting side encodes information using a
forward error correction code and then transmits the encoded
information. The receiving side demodulates a received signal and
decodes the error correction code to thereby recover the
information transmitted by the transmitting side. In this decoding
procedure, errors in the received signal caused by a channel are
corrected.
Data arrives at a coding block in the form of a maximum of two
transport blocks every transmission time interval (TTI) in each
DL/UL cell. The following coding steps may be applied to each
transport block of the DL/UL cell: cyclic redundancy check (CRC)
attachment to a transport block; code block segmentation and CRC
attachment to a code block; channel coding; rate matching; and code
block concatenation.
Although various types of error correction codes are available, a
turbo code has mainly been used in a legacy LTE/LTE-A system. The
turbo code is implemented by a recursive systematic convolution
encoder and an interleaver. For actual implementation of the turbo
code, an interleaver is used to facilitate parallel decoding and
quadratic polynomial permutation (QPP) is a kind of interleaving.
It is known that a QPP interleaver maintains good performance only
for a data block of a specific size. It is known that performance
of the turbo code increases with a larger data block size. In an
actual communication system, a data block of a predetermined size
or larger is divided into a plurality of smaller data blocks and
then is encoded, to facilitate actual implementation of coding. The
smaller data blocks are called code blocks. While the code blocks
are generally of the same size, one of the code blocks may have a
different size due to a limited size of the QPP interleaver. Error
correction coding is performed on each code block of a
predetermined interleaver size and then interleaving is performed
to reduce the impact of burst errors that are generated during
transmission over a radio channel. The error-corrected and
interleaved code block is transmitted by being mapped to an actual
radio resource. The amount of radio resources used for actual
transmission is designated. Thus, the encoded code blocks are
rate-matched to the amount of the radio resources. In general, rate
matching is performed through puncturing or repetition. For
example, if the amount of radio resources, i.e., the number of
transmission bits capable of being transmitted on the radio
resources, is M and if a coded bit sequence, i.e., the number of
output bits of the encoder, is N, in which M is different from N,
then rate matching is performed to match the length of the coded
bit sequence to M. If M>N, then all or a part of bits of the
coded bit sequence are repeated to match the length of the
rate-matched sequence to M. If M<N, then a part of the bits of
the coded bit sequence is punctured to match the length of the
rate-matched sequence to M and the punctured bits are excluded from
transmission.
Namely, in an LTE/LTE-A system, after data to be transmitted is
encoded using channel coding having a specific code rate (e.g.,
1/3), the code rate of the data to be transmitted is adjusted
through a rate-matching procedure consisting of puncturing and
repetition. When the turbo code is used as a channel code in the
LTE/LTE-A system, a procedure of performing channel coding and
rate-matching on each code block in the transport block processing
procedure as illustrated in FIG. 1 is illustrated in FIG. 2.
FIG. 2 is a block diagram illustrating rate matching performed by
separating an encoded code block into a systematic part and a
parity part.
As illustrated in FIG. 2, the mother code rate of an LTE/LTE-A
turbo encoder is 1/3. In order to obtain other code rates, if
necessary, repetition or puncturing has to be performed, which are
performed by a rate matching module. The rate matching module
consists of three so-called sub-block interleavers for three output
streams of the turbo encoder and a bit selection and pruning part,
which is realized by a circular buffer. The sub-block interleaver
is based on a classic row-column interleaver with 32 rows and
length-32 intra-column permutation. The bits of each of the three
streams are written row-by-row into a matrix with 32 columns
(number of rows depends on stream size). Dummy bits are padded to
the front of each stream to completely fill the matrix. After
column permutation, bits are read out from the matrix
column-by-column.
FIG. 3 illustrates an internal structure of a circular buffer.
The circular buffer is the most important part of the rate matching
module, making it possible to perform puncturing and repetition of
a mother code. Referring to FIG. 2, the interleaved systematic bits
are written into the circular buffer in sequence, with the first
bit of the interleaved systematic bit stream at the beginning of
the buffer. The interleaved and interlaced parity bit streams are
written into the buffer in sequence, with the first bit of the
stream next to the last bit of the interleaved systematic bit
stream. Coded bits (depending on code rate) are read out serially
from a certain starting point specified by redundancy version (RV)
points in the circular buffer. If the coded bits reaches the end of
the circular buffer and more coded bits are needed for transmission
(in the case of a code rate smaller than 1/3), a transmitting
device wraps around and continues at the beginning of the circular
buffer.
HARQ, which stands for Hybrid ARQ, is an error correction mechanism
based on retransmission of packets, which are detected with errors.
The transmitted packet arrives at a receiving device after a
certain propagation delay. The receiving device produces ACK for
the case of error-free transmission or NACK for the case of
detection of some errors. ACK/NACK is produced after some
processing time and sent back to the transmitting device and
arrives at the transmitting device after a propagation delay. In
the case of NACK, after a certain processing delay in the
transmitting device, a desired packet will be sent again. Bits,
which are read out from the circular buffer and sent through
retransmission, are different and depend on the position of the RV.
There are four RVs (0, 1, 2, and 3), which define the position of a
starting point at which the bits are read out from the circular
buffer. Referring to FIG. 3, with the progressing number of
retransmissions, the RV becomes higher and therefore fewer
systematic bits and more parity bits are read out from the circular
buffer for retransmission.
NR provides higher speeds and better coverage than current 4G. NR
operates in a high frequency band and is required to offer speeds
of up to 1 Gb/s for tens of connections or tens of Mb/s for tens of
thousands of connections. To meet requirements of such an NR
system, introduction of a more evolved coding scheme than a legacy
coding scheme is under discussion. Since data communication arises
in an incomplete channel environment, channel coding plays an
important role in achieving a higher data rate for fast and
error-free communication. A selected channel code needs to provide
superior block error ratio (BLER) performance for block lengths and
code rates of a specific range. Herein, BLER is defined as the
ratio of the number of erroneous received blocks to the total
number of sent blocks. In NR, low calculation complexity, low
latency, low cost, and higher flexibility are demanded for a coding
scheme. Furthermore, reduced energy per bit and improved region
efficiency are needed to support a higher data rate. Use examples
for NR networks are enhanced mobile broadband (eMBB), massive
Internet of things (IoT), and ultra-reliable and low latency
communication (URLLC). eMBB covers Internet access with high data
rates to enable rich media applications, cloud storage and
applications, and augmented reality for entertainment. Massive IoT
applications include dense sensor networks for smart
homes/buildings, remote health monitoring, and logistics tracking.
URLLC covers critical applications that demand ultra-high
reliability and low latency, such as industrial automation,
driverless vehicles, remote surgery, and smart grids.
Although many coding schemes with high capacity performance at
large block lengths are available, many of these coding schemes do
not consistently exhibit excellent good performance in a wide range
of block lengths and code rates. However, turbo codes, low-density
parity check (LPDC) codes, and polar codes show promising BLER
performance in a wide range of coding rates and code lengths and
hence are considered to be used in the NR system. As demand for
various cases such as eMBB, massive IoT, and URLLC has increased, a
coding scheme providing greater channel coding efficiency than in
turbo codes is needed. In addition, increase in a maximum number of
subscribers capable of being accommodated by a channel, i.e.,
increase in capacity, has been required.
Polar codes are codes providing a new framework capable of solving
problems of legacy channel codes and were invented by Arikan at
Bilkent University (reference: E. Arikan, "Channel Polarization: A
Method for Constructing Capacity-Achieving Codes for Symmetric
Binary-Input Memoryless Channels," in IEEE Transactions on
Information Theory, vol. 55, no. 7, pp. 3051-3073, July 2009).
Polar codes are the first capacity-achieving codes with low
encoding and decoding complexities, which were proven
mathematically. Polar codes outperform the turbo codes in large
block lengths while no error flow is present. Hereinafter, channel
coding using the polar codes is referred to as polar coding.
Polar codes are known as codes capable of achieving the capacity of
a given binary discrete memoryless channel. This can be achieved
only when a block size is sufficiently large. That is, polar codes
are codes capable of achieving the capacity of a channel if the
size N of the codes infinitely increases. Polar codes have low
encoding and decoding complexity and may be successfully decoded.
Polar codes are a sort of linear block error correction codes.
Multiple recursive concatenations are basic building blocks for the
polar codes and are bases for code construction. Physical
conversion of channels in which physical channels are converted
into virtual channels occurs and such conversion is based on a
plurality of recursive concatenations. If multiple channels are
multiplied and accumulated, most of the channels may become better
or worse. The idea underlying polar codes is to use good channels.
For example, data is sent through good channels at rate 1 and data
is sent through bad channels at rate 0. That is, through channel
polarization, channels enter a polarized state from a normal
state.
FIG. 4 is a block diagram for a polar code encoder.
FIG. 4(a) illustrates a base module of a polar code, particularly,
first level channel combining for polar coding. In FIG. 4(a),
W.sub.2 denotes an entire equivalent channel obtained by combining
two binary-input discrete memoryless channels (B-DMCs), Ws. Herein,
u.sub.1 and u.sub.2 are binary-input source bits and y.sub.1 and
y.sub.2 are output coded bits. Channel combining is a procedure of
concatenating the B-DMCs in parallel.
FIG. 4(b) illustrates a base matrix F for the base module. The
binary-input source bits u.sub.1 and u.sub.2 input to the base
matrix F and the output coded bits x.sub.1 and x.sub.2 of the base
matrix F have the following relationship.
.times..function..times..times..times. ##EQU00001##
The channel W.sub.2 may achieve symmetric capacity I(W) which is a
highest rate. In the B-DMC W, symmetric capacity is an important
parameter which is used to measure a rate and is a highest rate at
which reliable communication can occur over the channel W. The
B-DMC may be defined as follows.
.function..di-elect cons..times. .di-elect
cons..times..times..function..times..times..function..times..function..ti-
mes..function..times..times. ##EQU00002##
It is possible to synthesize or create a second set of N binary
input channels out of N independent copies of a given B-DMC W and
the channels have the properties {W.sub.N.sup.(i):
1.ltoreq.i.ltoreq.N}. If N increases, there is a tendency for a
part of the channels to have capacity approximating to 1 and for
the remaining channels to have capacity approximating to 0. This is
called channel polarization. In other words, channel polarization
is a process of creating a second set of N channels
{W.sub.N.sup.(i): 1.ltoreq.i.ltoreq.N} using N independent copies
of a given B-DMC W. The effect of channel polarization means that,
when N increases, all symmetric capacity terms {I(W.sub.N.sup.(i)}
tend towards 0 or 1 for all except a vanishing fraction of indexes
i. In other words, the concept behind channel polarization in the
polar codes is transforming N copies (i.e., N transmissions) of a
channel having a symmetric capacity of I(W) (e.g., additive white
Gaussian noise channel) into extreme channels of capacity close to
1 or 0. Among the N channels, an I(W) fraction will be perfect
channels and an 1-I(W) fraction will be completely noise channels.
Then, information bits are transmitted only through good channels
and bits input to the other channels are frozen to 1 or 0. The
amount of channel polarization increases along with a block length.
Channel polarization consists of two phases: channel combining
phase and channel splitting phase.
FIG. 5 illustrates the concept of channel combining and channel
splitting for channel polarization. As illustrated in FIG. 5, when
N copies of an original channel W are properly combined to create a
vector channel W.sub.vec and then are split into new polarized
channels, the new polarized channels are categorized into channels
having capacity C(W)=1 and channels having C(W)=0 if N is
sufficiently large. In this case, since bits passing through the
channels having the channel capacity C(W))=1 are transmitted
without error, it is better to transmit information bits
therethrough and, since bits passing through the channels having
capacity C(W)=1 cannot transport information, it is better to
transport frozen bits, which are meaningless bits,
therethrough.
Referring to FIG. 5, copies of a given B-DMC W are combined in a
recursive manner to output a vector channel W.sub.vec given by
X.sub.N.fwdarw.Y.sub.N, where N=2.sup.n and n is an integer equal
to or greater than 0. Recursion always begins at the 0th level and
W.sub.1=W. If n is 1 (n=1), this means the first level of recursion
in which two independent copies of W.sub.1 are combined. If the
above two copies are combined, a channel W.sub.2:
X.sub.2.fwdarw.Y.sub.2 is obtained. A transitional probability of
this new channel W.sub.2 may be represented by the following
equation.
W.sub.2(y.sub.1y.sub.2|u.sub.1,u.sub.2)=W(y.sub.1|u.sub.1.sym.u.sub.2)W(y-
.sub.1|u.sub.2) Equation 3
If the channel W.sub.2 is obtained, two copies of the channel
W.sub.2 are combined to obtain a single copy of a channel W.sub.4.
Such recursion may be represented by W.sub.4:
X.sub.4.fwdarw.Y.sub.4 having the following transitional
probability.
W.sub.4(y.sub.1.sup.4|u.sub.1.sup.4)=W.sub.2(y.sub.1.sup.2|u.sub.1.sym.u.-
sub.2,u.sub.3.sym.u.sub.4)W.sub.2(y.sub.3.sup.4|u.sub.2,u.sub.4)
Equation 4
In FIG. 5, G.sub.N is a size-N generator matrix. G.sub.2
corresponds to the base matrix F illustrated in FIG. 4(b). G.sub.4
may be represented by the following matrix.
.function..times..times. ##EQU00003##
Herein, .quadrature. denotes the Kronecker product,
A.sup..quadrature.n=A.quadrature.A.sup..quadrature.(n-1) for all
n.gtoreq.1, and A.sup..quadrature.0=1.
The relationship between input u.sup.N.sub.1 to G.sub.N and output
x.sup.N.sub.1 of G.sub.N of FIG. 5(b) may be represented as
x.sup.N.sub.1=u.sup.N.sub.1G.sub.N, where x.sup.N.sub.1={x.sub.1, .
. . , x.sub.N}, u.sup.N.sub.1=(u.sub.1, . . . , u.sub.N).
When N B-DMCs are combined, each B-DMC may be expressed in a
recursive manner.
That is, G.sub.N may be indicated by the following equation.
G.sub.N=B.sub.NF.sup..sym.n Equation 6
Herein, N=2.sup.n, n.gtoreq.1,
F.sup..quadrature.n=F.quadrature.F.sup..quadrature.(n-1), and
F.sup..quadrature.0=1. B.sub.N is a permutation matrix known as a
bit-reversal operation and
B.sub.N=R.sub.N(I.sub.2.quadrature.B.sub.N/2) and may be
recursively computed. I.sub.2 is a 2-dimensional identity matrix
and this recursion is initialized to B.sub.2=I.sub.2. R.sub.N is a
bit-reversal interleaver and is used to map an input
s.sup.N.sub.1={s.sub.1, . . . , s.sub.N} to an output
X.sup.N.sub.1={s.sub.1, s.sub.3, . . . , s.sub.N-1, s.sub.2, . . .
, s.sub.N}. The bit-reversal interleaver may not be included in a
transmitting side. The relationship of Equation is illustrated in
FIG. 6.
FIG. 6 illustrates N-th level channel combining for a polar
code.
A process of defining an equivalent channel for specific input
after combining N B-DMCs Ws is called channel splitting. Channel
splitting may be represented as a channel transition probability
indicated by the following equation.
.function..times..times..function..times..times. ##EQU00004##
Channel polarization has the following characteristics:
>Conservation: C(W.sup.-)+C(W.sup.+)=2C(W),
>Extremization: C(W.sup.-).ltoreq.C(W).ltoreq.C(W.sup.+).
When channel combining and channel splitting are performed, the
following theorem may be obtained. Theorem: For any B-DMC W,
channels {W.sub.N.sup.(i)} are polarized in the following sense.
For any fixed .delta..quadrature.{0,1}, as N goes to infinity
through powers of 2, the fraction of indexes i.di-elect cons.{1, .
. . , N} for channel capacity
I(W.sub.N.sup.(i)).quadrature.(1-.delta.,1] goes to I(W) and the
faction of i for channel capacity
I(W.sub.N.sup.(i).quadrature.[0,.delta.) goes to 1-I(W). Hence, if
N.fwdarw..infin., then channels are perfectly noisy or are
polarized free of noise. These channels can be accurately
recognized by the transmitting side. Therefore, bad channels are
fixed and non-fixed bits may be transmitted on good channels.
That is, if the size N of polar codes is infinite, a channel has
much noise or is free of noise, with respect to a specific input
bit. This has the same meaning that the capacity of an equivalent
channel for a specific input bit is divided into 0 or I(W).
Inputs of a polar encoder are divided into bit channels to which
information data is mapped and bit channels to which the
information data is not mapped. As described earlier, according to
the theorem of the polar code, if a codeword of the polar code goes
to infinity, the input bit channels may be classified into
noiseless channels and noise channels. Therefore, if information is
allocated to the noiseless bit channels, channel capacity may be
obtained. However, in actuality, a codeword of an infinite length
cannot be configured, reliabilities of the input bit channels are
calculated and data bits are allocated to the input bit channels in
order of reliabilities. In the present invention, bit channels to
which data bits are allocated are referred to as good bit channels.
The good bit channels may be input bit channels to which the data
bits are mapped. Bit channels to which data is not mapped are
referred to as frozen bit channels. A known value (e.g., 0) is
input to the frozen bit channels and then encoding is performed.
Any values which are known to the transmitting side and the
receiving side may be mapped to the frozen bit channels. When
puncturing or repetition is performed, information about the good
bit channels may be used. For example, positions of codeword bits
(i.e., output bits) corresponding to positions of input bits to
which information bits are not allocated may be punctured.
A decoding scheme of the polar codes is a successive cancellation
(SC) decoding scheme. The SC decoding scheme obtains a channel
transition probability and then calculates a likelihood ratio (LLR)
of input bits using the channel transition probability. In this
case, the channel transition probability may be calculated in a
recursive form if channel combining and channel splitting
procedures use characteristics of the recursive form. Therefore, a
final LLR value may also be calculated in the recursive form.
First, a channel transition probability
W.sub.N.sup.(i)(y.sub.1.sup.N, u.sub.1.sup.i-1|u.sub.1) of an input
bit u.sub.i may be obtained as follows. u.sub.1.sup.i may be split
into odd indexes and even indexes as expressed as u.sub.1,o.sup.i,
u.sub.1,e.sup.1, respectively. The channel transition probability
may be indicated by the following equations.
.times..times..function..times..times..times..times..times..times..times.-
.times..times..function..times..times..times..times..times..times..times..-
times..times..function..times..sym..times..times..function..times..times..-
times..times..times..times..times..times..times..function..times..times..t-
imes..times..times..times..function..times..sym..times..times..times..time-
s..times..function..times..sym..times..times..sym..times..function..times.-
.times..times..times..times..times..times..times..function..times..times..-
function..times..times..times..times..function..times..times..times.
.times..times..times..times..times..times..times..function..times..times.
.times..times..times..times..times..times..times..times..function..times-
..sym..times..times..function..times..times..times..times..times..times..t-
imes..times..function..times..times..times..times..times..times..times..fu-
nction..times..sym..times..times..function..times..sym..times..times..sym.-
.times..function..times..times..times..times..times..times.
##EQU00005##
A polar decoder retrieves information and generates an estimate
u{circumflex over ( )}.sup.N.sub.1 of u.sup.N.sub.1 using values
(e.g., reception bits, frozen bits, etc.) known for the polar
codes. The LLR is defined as follows.
.function..function..function..times..times. ##EQU00006##
The LLR may be recursively calculated as follows.
.times..function..times..function..times..sym..times..function..times..fu-
nction..times..sym..times..function..times..times..times..times..function.-
.times..function..times..sym..times..times..times..function..times..times.-
.times. ##EQU00007##
Recursive calculation of LLRs is traced back to a code length of 1
with an LLR L.sup.(1).sub.1(y.sub.i)=W(y.sub.i|0)/W(y.sub.i).
L.sup.(1).sub.1(y.sub.i) is soft information observed from a
channel.
The complexity of a polar encoder and an SC decoder varies with the
length N of polar codes and is known as having O(NlogN). Assuming
that K input bits are used for a length-N polar code, a coding rate
becomes N/K. If a generator matrix of a polar encoder of a data
payload size N is G.sub.N, an encoded bit may be represented as
x.sup.N.sub.1=u.sup.N.sub.1G.sub.N. Itis assumed that Kbits out of
u.sup.N.sub.1 correspond to payload bits, a row index of G.sub.N
corresponding to the payload bits is i, and a row index of G.sub.N
corresponding to (N-K) bits is F. A minimum distance of the polar
codes may be given as
d.sub.min(C)=min.sub.i.quadrature.I2.sup.wt(i), where wt(i) is the
number of 1s within binary extension of i and i=0, 1, . . . ,
N-1.
SC list (SCL) decoding is an extension of a basic SC decoder. In
this type of decoder, L decoding paths are simultaneously
considered in each decoding stage. Herein, L is an integer. In
other words, in the case of the polar codes, a list-L decoding
algorithm is an algorithm for simultaneously tracking L paths in a
decoding process.
FIG. 7 illustrates an evolution of decoding paths in a list-L
decoding process. For convenience of description, it is assumed
that the number of bits that should be determined is n and all bits
are not frozen. If a list size L is 4, each level includes at most
4 nodes with paths that continue downward. Discontinued paths are
expressed by dotted lines in FIG. 7. A process in which decoding
paths evolve in list-L decoding will now be described with
reference to FIG. 7. i) If list-L decoding is started, the first
unfrozen bit may be either 0 or 1. ii) list-L decoding continues.
The second unfrozen bits may be either 0 or 1. Since the number of
paths is not greater than L=4, pruning is not needed yet. iii)
Consideration of all options for the first bit (i.e., a bit of the
first level), the second bit (i.e. a bit of the second level), and
the third bit (i.e., a bit of the third level) results in 8
decoding paths which are excessive because L=4. iv) the 8 decoding
paths are pruned to L (=4) promising paths. v) 4 active paths
continue by considering two options of the fourth unfrozen bit. In
this case, the number of paths is doubled, i.e., 8 paths which are
excessive because L=4. vi) The 8 paths are pruned back to L (=4)
best paths. In the example of FIG. 7, 4 candidate codewords 0100,
0110, 0111, and 1111 are obtained and one of the codewords is
determined to be a codeword most similar to an original codeword.
In a similar manner to a normal decoding process, for example, in a
pruning process or a process of determining a final codeword, a
path in which the sum of LLR absolute values is largest may be
selected as a survival path. If a CRC is present, the survival path
may be selected through the CRC.
Meanwhile, CRC-aided SCL decoding is SCL decoding using CRC and
improves the performance of polar codes. CRC is the most widely
used technique in error detection and error correction in the field
of information theory and coding. For example, if an input block of
an error correction encoder has K bits and the length of
information bits is k, and the length of CRC sequences is m bits,
then K=k+m. CRC bits are a part of source bits for an error
correction code. If the size of channel codes used for encoding is
N, a code rate R is defined as R=K/N. CRC aided SCL decoding serves
to detect an errorless path while a receiving device confirms a CRC
code with respect to each path. An SCL decoder outputs candidate
sequences to a CRC detector. The CRC detector feeds back a check
result in order to aid in determining a codeword.
Although complicated as compared with an SC algorithm, SCL decoding
or CRC aided SCL decoding has an advantage of excellent decoding
performance. For more details of a list-X decoding algorithm of the
polar codes, refer to `I. Tal and A. Vardy, "List decoding of polar
codes," in Proc. IEEE Int. Symp. Inf. Theory, pp. 1-5, July
2011`.
In the polar codes, code design is independent of a channel and
hence is not versatile for mobile fading channels. In addition, the
polar codes have a disadvantage of limited application because the
codes have recently been introduced and have not grown yet. That
is, polar coding proposed up to now has many parts that have not
been defined to apply to a wireless communication system.
Therefore, the present invention proposes a polar coding method
suitable for the wireless communication system.
FIG. 8 illustrates the concept of selecting position(s) to which
information bit(s) are to be allocated in polar codes.
In FIG. 8, it is assumed that the size N of mother codes is 8,
i.e., the size N of polar codes is 8, and a code rate is 1/2.
In FIG. 8, C(W.sub.i) denotes the capacity of a channel W.sub.1 and
corresponds to the reliability of channels that input bits of a
polar code experience. When channel capacities corresponding to
input bit positions of the polar code are as illustrated in FIG. 8,
reliabilities of the input bit positions are ranked as illustrated
in FIG. 8. To transmit data at a code rate of 1/2, a transmitting
device allocates 4 bits constituting the data to 4 input bit
positions having high channel capacities among 8 input bit
positions (i.e., input bit positions denoted as U.sub.4, U.sub.6,
U.sub.7, and U.sub.4 among input bit positions U.sub.1 to U.sub.8
of FIG. 8) and freezes the other input bit positions. A generator
matrix G.sub.8 corresponding to the polar code of FIG. 8 is as
follows. The generator matrix G.sub.8 may be acquired based on
Equation 6.
.times..times..function..times..times..times..times..times..times..times.-
.times..times..function..times..times..times..times..times..times..times..-
times..times..function..times..sym..times..times..function..times..times..-
times..times..times..times..times..times..times..function..times..times..t-
imes..times..times..times..function..times..sym..times..times..times..time-
s..function..times..sym..times..times..sym..times..function..times..times.-
.times..times..times..times..times..times..function..times..times..functio-
n..times..times. ##EQU00008##
The input bit positions denoted as U.sub.1 to U.sub.8 of FIG. 8
correspond one by one to rows from the lowest row to the highest
row of G.sub.8. Referring to FIG. 8, it may be appreciated that the
input bit corresponding to U.sub.8 affects all output coded bits.
On the other hand, it may be appreciated that the input bit
corresponding to U.sub.1 affects only Y.sub.1 among the output
coded bits. Referring to Equation 12, when binary-input source bits
U.sub.1 to U.sub.8 are multiplied by G.sub.8, a row in which the
input bits appear at all output bits is the lowest row [1, 1, 1, 1,
1, 1, 1, 1] in which all elements are 1, among rows of G.sub.8.
Meanwhile, a row in which the binary-input source bits appears at
only one output bit is a row in which one element is 1 among the
rows of G.sub.8, i.e., a row [1, 0, 0, 0, 0, 0, 0, 0] in which a
row weight is 1. Similarly, it may be appreciated that a row in
which a row weight is 2 reflects input bits corresponding to the
row in two output bits. Referring to FIG. 8 and Equation 12,
U.sub.1 to U.sub.8 correspond one by one to the rows of G.sub.8 and
bit indexes for distinguishing between input positions of U.sub.1
to U.sub.8, i.e., bit indexes for distinguishing between the input
positions, may be assigned to the rows of G.sub.8.
Hereinafter, a description of the present invention will be given
focusing on the assumption that bit indexes from 0 to N-1 are
sequentially allocated to rows of G.sub.N starting from the highest
row having the smallest row weight with respect to N input bits.
For example, referring to FIG. 8, a bit index 0 is allocated to the
input position of U.sub.1, i.e., the first row of G.sub.8 and a bit
index 7 is allocated to the input position of U.sub.8, i.e., the
last row of G.sub.8. However, since the bit indexes are used to
indicate input positions of the polar code, a scheme different from
the above allocation scheme may be used. For example, bit indexes
from 0 to N-1 may be allocated staring from the lowest row having
the largest row weight.
In the case of output bit indexes, as illustrated in FIG. 8 and
Equation 12, the present invention will be described under the
assumption that bit indexes from 0 to N-1 or bit indexes from 1 to
N are assigned to columns from the first column having the largest
column weight to the last column having the smallest column weight
among columns of G.sub.N.
In the polar code, setting of information bits and frozen bits is
one of the most important elements in the configuration and
performance of the polar code. That is, determination of ranks of
input bit positions may be an important element in the performance
and configuration of the polar code. In the present invention, bit
indexes may distinguish input or output positions of the polar
code. In the present invention, a sequence obtained by enumerating
reliabilities of bit positions in ascending or descending order are
referred to as a bit index sequence. That is, the bit index
sequence represents reliabilities of input or output bit positions
of the polar code in ascending or descending order. A transmitting
device inputs information bits to input bits having high
reliabilities based on the input bit index sequence and performs
encoding using the polar code. A receiving device may discern input
positions to which information bits are allocated or input
positions to which frozen bits are allocated, using the same or
corresponding input bit index sequence. That is, the receiving
device may perform polar decoding using an input bit sequence which
is identical to or corresponds to an input bit index sequence used
by the transmitting device and using a corresponding polar code. In
the following description, it is assumed that an input bit sequence
is predetermined so that information bit(s) may be allocated to
input bit position(s) having high reliabilities.
A method of performing polar coding using a known bit as a frozen
bit and a method using `0` as the known bit are widely used. If
information other than `0` is transmitted at a frozen bit position,
the information transmitted at the frozen bit position has a
relatively low recovery probability because an input bit position
having a low reliability among input bit positions is usually used
as the frozen bit position. However, if information (hereinafter, a
reserved bit), which is already known through other channels, is
used as the frozen bit, a low recovery probability at a decoder may
have no problem. That is, since already known information does not
need to be included in a coded bit, the known information need not
be actually transmitted through channel coding. Hence, in the case
of the already known information, a recovery probability of
corresponding information is not important. Even when the reserved
bit is used as the frozen bit in the polar code, an error
probability of an information bit is not improved. However,
according to the proposal of the present invention, if a UE ID
(e.g., cell-radio network temporary identifier (C-RNTI)) is used as
the reserved bit, a false alarm ratio (FAR) in which a target UE ID
of a signal is mistaken for another UE ID may be improved. In the
present invention, the UE ID may be a UE ID of the transmitting
device performing polar encoding or may be a UE ID of the receiving
device performing polar decoding.
FIG. 9 illustrates puncturing and information bit allocation
according to the present invention. In FIG. 9, F denotes a frozen
bit, D denotes an information bit, and 0 denotes a skipping
bit.
Among coded bits, the case in which an information bit is changed
to a frozen bit may occur according to an index or position of a
punctured bit. For example, if output coded bits for a mother code
of N=8 should be punctured in order of Y8, Y7, Y6, Y4, Y5, Y3, Y2,
and Y1 and a target code rate is 1/2, then Y8, Y7, Y6, and Y4 are
punctured, U8, U7, U6, and U4 connected only to Y8, Y7, Y6, and Y4
are frozen to 0, and these input bits are not transmitted, as
illustrated in FIG. 9. An input bit changed to a frozen bit by
puncturing of a coded bit is referred to as a skipping bit or a
shortening bit and a corresponding input position is referred to as
a skipping position or a shortening position. Shortening is a rate
matching method of inserting a known bit into an input bit position
connected to a position of an output bit desired to be transmitted
while maintaining the size of input information (i.e., the size of
information blocks). Shortening is possible starting from input
corresponding to a column in which a column weight is 1 in a
generator matrix G.sub.N and next shortening may be performed with
respect to input corresponding to a column in which a column weight
is 1 in a remaining matrix from which a column and row in which a
column weight is 1 are removed. To prevent all information bits
from being punctured, an information bit that should have been
allocated to an information bit position may be reallocated in
order of a high reliability within a set of frozen bit
positions.
In the case of the polar code, decoding may be generally performed
in the following order.
>1. Bit(s) having low reliabilities are recovered. Although
reliability differs according to the structure of a decoder, since
an input index in an encoder (hereinafter, an encoder input index)
having a low value usually has a low reliability, decoding is
generally performed staring from a low encoder input index.
>2. When a known bit is present in a recovered bit, the known
bit is used together with the recovered bit or the process of 1 is
omitted and a known bit for a specific input bit position is
immediately used, thereby recovering an information bit, which is
an unknown bit. The information bit may be a source information bit
(e.g., a bit of a transport block) or a CRC bit.
FIG. 10 illustrates a polar encoding process and a polar decoding
process of the present invention for improving a false alarm ratio
(FAR).
Referring to FIG. 10(a), the polar encoding process according to
the present invention includes adding a CRC code/sequence to
information bits (S1011), adding reserved bit(s)(S1013), and then
performing polar encoding on CRC-added information bits and the
reserved bit(s) (S1015), thereby producing coded bits. The reserved
bits may be added to the front or end of the information bits or
may be inserted between the information bits. Alternatively, the
reserved bits may be masked to the information bits through an XOR
operation between the information bits and the reserved bits.
In the present invention, decoding may be performed in a reverse
order of the encoding process of FIG. 10(a). Referring to FIG.
10(b), a receiving device receiving the coded bits performs polar
decoding on the received bits (S1021) and obtains the decoded
bit(s). Next, the reserved bits may be used to check original
information of the decoded bits (S1023). For example, if the
reserved bits are a UE ID and a transmitting device masks the UE ID
to the input bits through an XOR operation between the UE ID and
the input bits, the receiving device may generate decoded bits with
which the UE ID is XORed. The receiving device compares the UE ID
obtained by recovering the received signal with an already known UE
ID to determine whether the received signal is information of the
receiving device (S1023). For example, if the UE ID obtained by
recovering the received signal is different from the UE ID of the
receiving device, the receiving device may determine that the
decoded signal is not a signal therefor. Further, the receiving
device may filter out the received signal once more by determining
decoding success/failure through a CRC (S1025). For example, the
receiving device may confirm whether a result of comparison between
the UE ID thereof and the decoded UE ID is a proper result through
the CRC.
In the present invention, positions of the reserved bits may be
selected/determined as follows and may be differently
selected/determined as needed. Option 1. Since decoding is
performed starting from a bit having the lowest reliability,
reserved bit(s) may be positioned starting from a bit position
having the lowest reliability. Option 2. The reserved bit(s) may be
positioned at bit(s) having the highest reliability among frozen
bits. In other words, the reserved bit(s) may be positioned at
frozen bit position(s) in descending order of reliability starting
from a bit position having the highest reliability among input
positions to which frozen bits are allocated. This method may
reduce an FAR by allocating the reserved bits to bits having the
highest recovery probability among the frozen bits. Option 3. The
reserved bit(s) may be positioned at bit(s) having the highest
reliability among information bits. In other words, the reserved
bit(s) may be positioned at information bit position(s) in
descending order of reliability starting from a bit position having
the highest reliability among input positions to which information
bits (including a CRC bit) are allocated. The information bits may
be input to input bit positions having relatively high
reliabilities among the other input bit positions except for input
bit position(s) occupied by the reserved bit(s). According to this
method, since a recovery probability of the reserved bit(s) is
highest among all bits, the method may serve to reduce the FAR when
the CRC is limited.
When the reserved bits are allocated to input bit positions
according to Option 1, Option 2, and/or Option 3, all or a part of
the reserved bits may be allocated. Alternatively, two or more of
Option 1, Option 2, and Option 3 may be used according to priority
of the reserved bits. When the UE ID is used as the reserved bits,
since it is inefficient to allocate only a part of the UE ID to the
input bit positions, it may be impossible to allocate the UE ID to
the input positions by the above option(s) if the size of frozen
bits to which all of the UE ID is to be allocated is not secured.
In this case, masking for information bit(s) using the UE ID (e.g.,
XOR between the UE and the information bit(s)) may be
performed.
The present invention may perform masking for the reserved bits to
a part of coded bits. In this case, since a UE which does not the
reserved bits cannot demask a masked reception signal, an error
probability of decoded bits increases and thus decoding performance
deteriorates. Hence, the present invention can reduce the
probability, i.e., the FAR, that a UE not having the reserved bits
used for masking in the transmitting device or a UE using other
reserved bits mistakes signals for other UEs for signals therefor.
Positions to which the reserved bit(s) are allocated may be
determined according to reliability of coded bits.
In the present invention, the reserved bit(s), e.g., the UE ID, may
aid in performing early termination of decoding in order to reduce
decoding latency. Hypothesis decision using a path metric for a
list size during polar decoding (see `R1-1706194, "On channel
coding for very small control block lengths," Huawei, RAN1 #88bis`)
has been proposed as an implementation scheme for early
termination. The early termination scheme according to the
hypothesis decision may be performed as follows. Notations used to
describe the hypothesis decision are as follows. N: codeword
length. K: information block length (e.g., the size of transport
blocks). L: list size of polar decoder. PM[i,1], i=1, 2, . . . , N,
1=1, 2, . . . , L: i-th path metric for i-th input index. The sum
of path metrics is normalized such that a maximum value is 1.
i.sub.TH: start input index to check early termination criterion.
.DELTA.: window size to check early termination criterion. Thr:
threshold value for early termination. max: function to fine
maximum value of arguments.
Early termination may be performed using path metrics with the
following criterion.
>For decoding index i.sub.THi=.sub.TH+.DELTA., check if
max{PM[i,1]}>Thr.
>If the above condition fails, stop decoding and declare an
error.
When CRC bit(s) or parity bit(s) are added to the early termination
scheme, decoding may be performed as follows. For example, assuming
that a 3-bit CRC is used, decoding may be performed as follows.
>at decoding index i*,
>>perform 3 cyclic redundancy checks (hereinafter, CRC-check)
with some parts of information bits+CRC bits, i.e., using parts of
information bits and CRC bits;
>>check if max.sub.1.quadrature.B{PM[i*,1]}>Thr (condition
2) where B includes path indexes to pass the CRC-check;
>>stop decoding when either "all paths fail to perform the
CRC-check" or "condition 2" fails.
FIG. 11 illustrates BLER performance and an early termination
probability for polar encoding/decoding according to the present
invention.
Only when a UE ID is correctly decoded, a receiving device can
confirm whether a received signal is information thereof and thus
can effectively perform early termination. Assuming that
performance of UE ID decoding does not deteriorate, since BLER
performance of the present invention having early termination is
identical to legacy BLER performance without early termination as
illustrated in FIG. 11(a), path metric based early termination may
be implemented according to the present invention without degrading
BLER performance. As illustrated in FIG. 11(a), an early
termination probability of a legacy polar encoding/decoding method
is `0`, whereas the present invention can obtain the early
termination probability as illustrated in FIG. 11(b) even when
there is no degradation in BLER performance in the present
invention. Therefore, in the present invention, the receiving
device may quickly recognize that received information is not
information therefor upon receiving information for other receiving
devices and may terminate decoding.
A recovery probability of a UE ID may differ according to a
position to which a bit of the UE ID is allocated. Since a polar
decoder performs decoding starting from a position having a low
reliability among frozen bits, a trade-off between a BLER and
average latency may occur according to a UE ID position. Option a.
The UE ID may be positioned at a side having the lowest reliability
among frozen bits. That is, the UE ID may be positioned at
positions having the lowest reliability among frozen bit positions.
In this case, since the BLER of the UE ID is relatively low, an
early termination probability may be high. Since early termination
may be performed after the UE ID is decoded, latency may be lowest.
Option b. The UE ID may be positioned at a side having the highest
reliability among frozen bits. That is, the UE ID may be positioned
at positions having the highest reliability among frozen bit
positions. In this case, the BLER is better than in Option a but
the early termination probability may be lower than Option a and
decoding latency may increase as compared with Option a. Option c.
The UE ID may be positioned at a side having a middle reliability
among the frozen bits. That is, the UE ID may be positioned at
positions having a middle reliability among the frozen bit
positions. Option c has characteristics of a medium between Option
a and Option b. Option d. The UE ID may be included in information
bit position(s). An information bit of an information bit position
to which the UE ID is allocated may move to a position having the
highest reliability among the frozen bit positions. For example,
when the number of information bits is N and the number of reserved
bits is 1, since one of N input bit positions having the highest
reliability is used for the reserved bit, the information bit
sequence except for an information bit that should be allocated to
an information bit position used by the reserved bit are allocated
to N-1 existing information bit positions and the information bit
that should have been allocated to the information bit position
used by the reserved bit may be allocated to a frozen bit position
having the highest reliability among the frozen bit positions.
Alternatively, the same number of bit positions having high
reliabilities among frozen bit positions as the number of
information bit positions to which the UE ID is allocated may be
changed to information bit positions. For example, when the number
of information bits is N and the number of reserved bits is 1,
since one of N input bit positions having the highest reliability
is used for the reserved bit, an information bit sequence is
sequentially allocated to the other positions except for an
information bit position used by the reserved bit and the last one
bit of the information bit sequence may be allocated to a frozen
bit position having the highest reliability among the frozen bit
positions. BLER may be worsened due to an information bit moving to
an original frozen bit position. However, since the reliability of
the UE ID increases, the BLER of the UE ID may be raised. If the
BLER of the UE ID is raised, signals for the receiving device may
be clearly distinguished from signals for other users upon
performing blind detection for the signals (e.g., control channels)
directed to the receiving device. Option e. The UE ID may be
positioned at a side having the lowest reliability among
information bits. That is, the UE ID may be positioned at positions
having the lowest reliability among information bit positions. In
this case, since a code rate is raised, BLER may be lowered.
However, since the reliability of the UE ID increases, the BLER of
the UE ID may be raised. In addition, since the UE ID is positioned
at an information bit position, FAR performance may be raised
through CRC-check. Alternatively, since the UE ID is positioned at
the information bit position, signals for the receiving device may
be clearly distinguished from signals for other users upon
performing blind detection for the signals (e.g., control channels)
directed to the receiving device.
An (allocation) position of the UE ID may be determined according
to requirements of a system to which the present invention is
applied.
To raise an early termination effect, masking may be performed with
respect to a length of reserved or known bit(s) or more. Herein,
the UE ID may be used as the reserved or known bit(s). In addition,
a slot index (i.e., a time resource unit index) or information from
downlink control information (DCI) and/or uplink control
information (UCI) may be used as the reserved or known bit(s).
Hereinafter, the present invention will be described under the
assumption that the UE ID is the reserved or known signal for
convenience of description.
In the present invention, the early termination effect can be
raised by increasing the length of the UE ID. The UE ID is fixed to
16 bits in the LTE/LTE-A system. When the length of the UE ID is
fixed to a specific length, a certain sequence including the UE ID,
longer than the specific length, may be used in the present
invention. In the present invention, a sequence in which the
reserved or known bit (e.g., UE ID) is included may be generated as
follows. Hereinafter, the present invention will be described by
referring to a sequence in which the reserved or known bit is
included as to a UE ID sequence.
FIG. 12 illustrates sequences in which reserved or known bit(s) of
the present invention are included. In FIG. 12, it is assumed that
the reserved or known bit(s) are a UE ID and the UE ID is a 4-bit
sequence ABCD consisting of A, B, C, and D of 4 bits.
Referring to FIG. 12(a) and FIG. 12(b), a UE ID sequence of a
desired length may be obtained by repeating the UE ID. If the
desired sequence length is not a multiple of an integer of the UE
ID, the UE ID sequence of a desired length may be obtained by
eliminating a part of the UE ID to be included in the last of the
sequence of the desired length and repeating the UE ID. FIG. 12(a)
illustrating the case in which the UE ID sequence is generated by
repeating the entire UE ID and FIG. 12(b) illustrates the case in
which the UE ID sequence is generated by sequentially repeating
each bit of the UE ID the number of specific times. The method
illustrated in FIG. 12(a) may include a method of inserting the UE
ID according to reliability of frozen bits for early termination.
For example, ABCD, ABCD, . . . may be sequentially mapped to frozen
bit positions according to reliability of frozen bit positions. In
this case, early termination is possible even when only one set of
ABCD rather than repetition of ABCD is decoded. When necessary, for
example, bits of the UE ID are mixed and repeated to generate the
UE ID sequence of a desired length according to an order of UE ID
bits for which decoding should be first performed. For example,
since reliability and a decoded order are not accurately equal,
even if ABCD corresponding to the UE ID is allocated by the
transmitting device based on reliability, an actually decoded order
in the receiving device may be ABBCCD and, in consideration of this
fact, the UE ID may be mixed and repeated in the form of ABBCCD in
the transmitting device.
The length of the UE ID may be extended using a well-known sequence
such as an m-sequence. In this case, in order to clearly
distinguish between UE ID sequences as the length of a UE ID
sequence becomes short, a sequence which is known as having good
performance (e.g., randomization performance) even when the length
of the UE ID sequence is short may be used. The UE ID sequence may
be generated in consideration of the UE ID (e.g., UE ID itself
and/or UE ID length), information length K, mother code length N,
codeword length M, and frozen bit length considering a rate
matching scheme. Thereamong, the same sequence may be used for some
parameters. In other words, some parameters among the UE ID, K, N,
M, and frozen bit length may not be used. For example, if K is not
used as a parameter, the same sequence is used even when K varies.
Not only the UE ID but also the slot index and the information from
the DCI and/or UCI may be used to generate the UE sequence and
various information may be simultaneously used to generate the UE
ID sequence. In addition, the UE ID sequence may be configured by
reflecting characteristics of a sequence such as an m-sequence. For
example, the UE ID sequence of a specific length may be obtained by
applying a different cyclic shift value according to the UE ID in a
similar way to the m-sequence. In other words, the length of the UE
ID sequence may vary according to UE IDs or UE ID groups and a
sequence generator may generate UE ID sequences of different
lengths using different cyclic shift values.
In the present invention, methods of masking the UE ID may be
broadly divided into two methods. Masking Method 1. Masking UE ID
to Frozen Bit Position(s)
According to masking Method 1, since a decoder may first decode a
frozen bit position, an early termination effect can be improved.
Since legacy frozen bits are all set to `0`, the UE ID sequence may
be inserted into frozen bit position(s). The UE ID sequence may be
generated as in FIG. 12(c) or FIG. 12(d) according to parameters
(e.g., UE ID, K, N, M, and frozen bit length). In addition, the UE
ID sequence may be generated as a maximum length according to some
parameters and then may be regenerated as a desired short length.
When it is assumed that the UE ID sequences illustrated in FIG.
12(a) and FIG. 12(b) are UE ID sequences of a maximum length, the
UE ID sequence of FIG. 12(c), shorter than the UE ID sequence of
FIG. 12(a), may be obtained from the UE ID sequence of FIG. 12(a)
and the UE ID sequence of FIG. 12(d), shorter than the UE ID
sequence of FIG. 12(b), may be obtained from the UE ID sequence of
FIG. 12(b). The UE ID sequence illustrated in FIG. 12(c) may be
obtained by eliminating the last or first part of the UE ID
sequence of a maximum length or by performing cyclic repetition so
that the UE ID sequence may have a desired length. The UE ID
sequence illustrated in FIG. 12(d) may be obtained by reducing the
number of repetitions for a part of the UE ID.
When a sequence is pre-generated by reflecting a rate matching
scheme, a sequence of a corresponding length is generated. However,
when a sequence is generated without considering the rate matching
scheme, the length of the sequence should be adjusted according to
the rate matching scheme. The method illustrated in FIG. 12(c) may
easily adjust the length of the sequence according to the rate
matching scheme. For example, when skipping occurs due to
puncturing, since the length of frozen bits is reduced by a length
corresponding to occurrence of skipping, the length of the UE ID
sequence may be adjusted according to the method illustrated in
FIG. 12(c). Masking Method 2. Masking to a Codeword of Polar
Code
The UE ID sequence may be masked to an output sequence of a polar
code, i.e., a codeword. Masking Method 2 in which the UE ID
sequence is masked to the codeword may vary depending on whether
masking is performed before or after rate matching is applied to
the codeword. If masking to the codeword is performed prior to rate
matching, rate matching is performed after a UE ID sequence of a
maximum length is masked to the codeword. If masking to the
codeword is performed after rate matching, a rate-matched codeword
is masked using a UE ID sequence having an adjusted length.
If a reserved or known sequence is masked only to a part of a
codeword, a position to which the reserved or known sequence (e.g.,
a UE ID or a UE ID sequence obtained from the UE ID) is masked may
be as follows.
A. Order of codeword(s) including relatively many frozen bits among
codewords: this method serves to increase a minimum distance
between a codeword part associated with a corresponding frozen bit
and the UE ID in order to perform early termination starting from a
frozen bit.
B. Order of codeword(s) including relatively many information bits
among codewords: this method serves to increase a minimum distance
between a codeword part associated with a corresponding information
bit and the UE ID in order to perform early termination starting
from an information bit.
When a known sequence is masked only to a partial codeword, the
length of the known sequence may be a length with which it is easy
to generate and apply the sequence. In this case, a maximum length
of the known sequence may not exceed the length of an actually
transmitted codeword. Alternatively, when the length of the known
sequence is longer than the length of the actually transmitted
codeword, masking may be applied prior to rate matching. For
example, if a length-N known sequence is applied to a length-M
(where N>M) codeword, a length-M sequence out of the known
sequence is masked to the codeword through an XOR operation and the
other length-(N-M) sequence and a part of the codeword may be
masked through the XOR operation. If rate matching is applied at
the transmitting side, some bits to which masking is applied are
punctured and hence an LLR value for the punctured bits among the
masked bits becomes `0` or infinity at the receiving side. If
masking is performed upon a bit, an LLR value at the receiving side
of which becomes `0`, i.e., if masking is performed upon a bit
punctured at the transmitting side, since the distance between UE
IDs (e.g., the distance between UE IDs for distinguishing between
users) is not influenced by masking, the same effect as the case in
which masking is not performed occurs. For example, when a sequence
of a short length is S1, a sequence of a long length is S2 and it
is desired to reduce S2 to S1 through rate matching, a new sequence
of a short length need not be produced and S1 may be obtained by
puncturing S2. However, when shortening with puncturing different
from simple puncturing is performed, since an LLR is not `0`,
(simple) puncturing may use a length-M sequence and puncturing with
shortening may use a length-N sequence, with respect to the same M.
That is, the length of a sequence applied may vary according to a
rate matching scheme. For example, puncturing may be divided based
on a predetermined code rate such that puncturing is performed with
respect to a code rate lower than the predetermined code rate and
puncturing with shortening is performed with respect to a code rate
higher than the predetermined code rate. Herein, puncturing with
shortening means that puncturing is performed in a codeword and
shortening is performed due to skipping at an input side of a polar
code. Skipping a specific input bit position means that an
information bit skips the specific input bit position and is
allocated to an input bit position having the next high
reliability. Shortening means that a known bit is allocated to a
skipped bit position. When puncturing is applied, since a bit
having an LLR of `0` in the receiving side occurs, the length of a
sequence used for masking may be reduced.
Masking may be performed upon both a frozen bit and a codeword. In
this case, the same sequence may be used. Alternatively, different
sequences may be used for masking of the frozen bit and masking of
the codeword in order to increase a minimum distance between UE
IDs.
In the present invention, `0` may be input, like a legacy scheme,
to frozen bit positions, except for a frozen bit position to which
a UE ID or a UE ID sequence is allocated or a frozen bit position
to which an information bit is input due to a UE ID or a UE ID
sequence allocated to an information bit position.
FIG. 13 is a block diagram illustrating elements of a transmitting
device 10 and a receiving device 20 for implementing the present
invention.
The transmitting device 10 and the receiving device 20 respectively
include Radio Frequency (RF) units 13 and 23 capable of
transmitting and receiving radio signals carrying information,
data, signals, and/or messages, memories 12 and 22 for storing
information related to communication in a wireless communication
system, and processors 11 and 21 operationally connected to
elements such as the RF units 13 and 23 and the memories 12 and 22
to control the elements and configured to control the memories 12
and 22 and/or the RF units 13 and 23 so that a corresponding device
may perform at least one of the above-described embodiments of the
present invention.
The memories 12 and 22 may store programs for processing and
controlling the processors 11 and 21 and may temporarily store
input/output information. The memories 12 and 22 may be used as
buffers.
The processors 11 and 21 generally control the overall operation of
various modules in the transmitting device and the receiving
device. Especially, the processors 11 and 21 may perform various
control functions to implement the present invention. The
processors 11 and 21 may be referred to as controllers,
microcontrollers, microprocessors, or microcomputers. The
processors 11 and 21 may be implemented by hardware, firmware,
software, or a combination thereof. In a hardware configuration,
application specific integrated circuits (ASICs), digital signal
processors (DSPs), digital signal processing devices (DSPDs),
programmable logic devices (PLDs), or field programmable gate
arrays (FPGAs) may be included in the processors 11 and 21.
Meanwhile, if the present invention is implemented using firmware
or software, the firmware or software may be configured to include
modules, procedures, functions, etc. performing the functions or
operations of the present invention. Firmware or software
configured to perform the present invention may be included in the
processors 11 and 21 or stored in the memories 12 and 22 so as to
be driven by the processors 11 and 21.
The processor 11 of the transmitting device 10 performs
predetermined coding and modulation for a signal and/or data
scheduled to be transmitted to the outside by the processor 11 or a
scheduler connected with the processor 11, and then transfers the
coded and modulated data to the RF unit 13. For example, the
processor 11 converts a data stream to be transmitted into K layers
through demultiplexing, channel coding, scrambling, and modulation.
The coded data stream is also referred to as a codeword and is
equivalent to a transport block which is a data block provided by a
MAC layer. One transport block (TB) is coded into one codeword and
each codeword is transmitted to the receiving device in the form of
one or more layers. For frequency up-conversion, the RF unit 13 may
include an oscillator. The RF unit 13 may include N.sub.t (where
N.sub.t is a positive integer) transmit antennas.
A signal processing process of the receiving device 20 is the
reverse of the signal processing process of the transmitting device
10. Under control of the processor 21, the RF unit 23 of the
receiving device 20 receives radio signals transmitted by the
transmitting device 10. The RF unit 23 may include N.sub.r (where
N.sub.r is a positive integer) receive antennas and frequency
down-converts each signal received through receive antennas into a
baseband signal. The processor 21 decodes and demodulates the radio
signals received through the receive antennas and restores data
that the transmitting device 10 intended to transmit.
The RF units 13 and 23 include one or more antennas. An antenna
performs a function for transmitting signals processed by the RF
units 13 and 23 to the exterior or receiving radio signals from the
exterior to transfer the radio signals to the RF units 13 and 23.
The antenna may also be called an antenna port. Each antenna may
correspond to one physical antenna or may be configured by a
combination of more than one physical antenna element. The signal
transmitted from each antenna cannot be further deconstructed by
the receiving device 20. An RS transmitted through a corresponding
antenna defines an antenna from the view point of the receiving
device 20 and enables the receiving device 20 to derive channel
estimation for the antenna, irrespective of whether the channel
represents a single radio channel from one physical antenna or a
composite channel from a plurality of physical antenna elements
including the antenna. That is, an antenna is defined such that a
channel carrying a symbol of the antenna can be obtained from a
channel carrying another symbol of the same antenna. An RF unit
supporting a MIMO function of transmitting and receiving data using
a plurality of antennas may be connected to two or more
antennas.
The transmitting device 10 may be configured to include a polar
encoder according to the present invention and the receiving device
20 may be configured to include a polar decoder according to the
present invention. For example, the processor 11 of the
transmitting device 10 may be configured to perform polar encoding
according to the present invention and the processor 21 of the
receiving device 20 may be configured to perform polar decoding
according to the present invention. That is, the polar encoder
according to the present invention may be configured as a part of
the processor 11 of the transmitting device 10 and the polar
decoder according to the present invention may be configured as a
part of the processor 21 of the receiving device 20.
In the present invention, the processor 11 of the transmitting
device 10 may be configured to input bits including D-bit
information and an X-bit UE ID to a part of N input bit positions
of a size-N polar code according to a specific bit allocation
sequence. The processor 11 may encode the input bits using the
polar code and control the RF unit 13 of the transmitting device 10
to transmit an encoded output sequence. The processor 11 may
include the polar encoder configured to perform polar encoding. The
polar encoder may include N input bit positions corresponding to N
input bit positions of the polar code and N output bit positions
corresponding to N output bit positions of the polar code.
The processor 11 may be configured to input the D-bit information
to D input bit positions having high reliabilities among the N
input bit positions and input the UE ID to input position(s) having
high reliabilities among input bit positions (hereinafter, frozen
bit positions) except for the D input bit positions having high
reliabilities.
Alternatively, the processor 11 may be configured to input the UE
ID to X information bit positions among the D input bit positions
having high reliabilities. The processor 11 may be configured to
input a part of the D-bit information to bit positions except for
the X information bit positions to which the UE ID is input among
the D input bit positions having high reliabilities and input the
other information bit(s) among the D-bit information to frozen bit
position(s) having high reliabilities among the frozen bit
positions. The other information bit(s) may be information bit(s)
corresponding to the input bit positions to which the UE ID is
input among the D-bit information. For example, if a sequence
arranging indexes of input bit positions in descending order of
reliabilities is {8, 7, 6, 5, 4, 3, 2, 1} and 8-bit information
will be input to the input bit positions in order of U8, U7, U6,
U5, U4, U3, U2, and U1 when the UE ID is not present and if the
processor 11 inserts the UE ID into input bit positions 6, 5, 4,
and 3, the processor 11 may input U8, U7, U2, and U1 among bits of
the 8-bit information to the input bit positions 8, 7, 2, and 1 and
input U6, U5, U4, and U3 among the bits of the 8-bit information to
frozen bit positions having relatively high reliabilities among
existing frozen bit positions. Alternatively, the other information
bit(s) may be information bit(s) positioned at the end of the D-bit
information. For example, the processor 11 may input U8, U7, U2,
and U1 among the bits of the 8-bit information to the input bit
positions 8, 7, 2, and 1 and input U4, U3, U2, and U1 which are
bits positioned at the end of the bits of the 8-bit information to
the frozen bit positions having relatively high reliabilities among
the existing frozen bit positions. The UE ID may be an UE ID of the
transmitting device or a UE ID of the receiving device, which is a
destination of the information.
As described above, the detailed description of the preferred
embodiments of the present invention has been given to enable those
skilled in the art to implement and practice the invention.
Although the invention has been described with reference to
exemplary embodiments, those skilled in the art will appreciate
that various modifications and variations can be made in the
present invention without departing from the spirit or scope of the
invention described in the appended claims. Accordingly, the
invention should not be limited to the specific embodiments
described herein, but should be accorded the broadest scope
consistent with the principles and novel features disclosed
herein.
INDUSTRIAL APPLICABILITY
The embodiments of the present invention are applicable to a base
station, a user equipment or other devices in a wireless
communication system.
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